golang 实践 ~ cache 库

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### cache 是一个带索引带超时的缓存库 目的在于优化代码结构,提供了若干实践。 https://github.com/weapons97/cache #### example ### 实践1 定义泛型函数 1.18 已经发布一段实践了。通过泛型函数。我们可以减少循环的使用,优化代码结构。下面分享几个泛型函数和代码上的实践。 #### Filter 函数 ```go // Filter filter one slice func Filter[T any](objs []T, filter func(obj T) bool) []T { res := make([]T, 0, len(objs)) for i := range objs { ok := filter(objs[i]) if ok { res = append(res, objs[i]) } } return res } ``` ```go // 测试[]int func TestFilter(t *testing.T) { ans := []int{2, 4, 6} a := []int{1, 2, 3, 4, 5, 6} b := Filter(a, func(i int) bool { return i%2 == 0 }) require.Equal(t, ans, b) spew.Dump(b) } // 结果 === RUN TestFilter ([]int) (len=3 cap=6) { (int) 2, (int) 4, (int) 6 } --- PASS: TestFilter (0.00s) PASS // NoSpace is filter func for strings func NoSpace(s string) bool { return strings.TrimSpace(s) != "" } // 测试[]sting func TestFilterNoSpace(t *testing.T) { ans1 := []string{"1", "2", "3"} a := []string{"", "1", "", "2", "", "3", ""} b := Filter(a, NoSpace) require.Equal(t, ans1, b) spew.Dump(b) } // 结果 === RUN TestFilterNoSpace ([]string) (len=3 cap=7) { (string) (len=1) "1", (string) (len=1) "2", (string) (len=1) "3" } --- PASS: TestFilterNoSpace (0.00s) PASS ``` #### Map 函数 ```go // Map one slice func Map[T any, K any](objs []T, mapper func(obj T) ([]K, bool)) []K { res := make([]K, 0, len(objs)) for i := range objs { others, ok := mapper(objs[i]) if ok { res = append(res, others...) } } return res } // 测试 []int -> []string func TestMap(t *testing.T) { ans := []string{"2", "4", "6", "end"} a := []int{1, 2, 3, 4, 5, 6} b := Map(a, func(i int) ([]string, bool) { if i == 6 { return []string{fmt.Sprintf(`%v`, i), `end`}, true } if i%2 == 0 { return []string{fmt.Sprintf(`%v`, i)}, true } else { return nil, false } }) require.Equal(t, ans, b) spew.Dump(b) } // 结果 === RUN TestMap ([]string) (len=4 cap=6) { (string) (len=1) "2", (string) (len=1) "4", (string) (len=1) "6", (string) (len=3) "end" } --- PASS: TestMap (0.00s) PASS ``` ### First 函数 ```go // First make return first for slice func First[T any](objs []T) (T, bool) { if len(objs) > 0 { return objs[0], true } return *new(T), false } func TestFirstInt(t *testing.T) { ans1, ans2 := 1, 0 a := []int{1, 2, 3, 4, 5, 6} b, ok := First(a) require.True(t, ok) require.Equal(t, ans1, b) spew.Dump(b) c := []int{} d, ok := First(c) require.False(t, ok) require.Equal(t, ans2, d) spew.Dump(d) } // result === RUN TestFirstInt (int) 1 (int) 0 --- PASS: TestFirstInt (0.00s) PASS func TestFirstString(t *testing.T) { ans1, ans2 := "1", "" a := []string{"1", "2", "3", "4", "5", "6"} b, ok := First(a) require.True(t, ok) require.Equal(t, ans1, b) spew.Dump(b) c := []string{} d, ok := First(c) require.False(t, ok) require.Equal(t, ans2, d) spew.Dump(d) } // result === RUN TestFirstString (string) (len=1) "1" (string) "" --- PASS: TestFirstString (0.00s) PASS ``` ### 实践2 带超时的cache - 某些情况下,我们删除过期的cache, 通过利用带超时的cache,简化代码 - cache 结构 github.com/weapons97/cache/cache.go ```go // 用辅助map删除 if apiRet.TotalCount > 0 { var hc sync.Map for _, h := range apiRet.Hcis { hc.Store(h.HostID, h) hostCpu.Store(h.HostID, h) } hostCpu.Range(func(key, _ interface{}) bool { _, ok := hc.Load(key) if !ok { hostCpu.Delete(key) } return true }) } // 直接设置,过期的key 会删除 for _, h := range apiRet.Hcis { hostCpu.Set(h.HostID, h) } ``` ```go func TestNewCache(t *testing.T) { c := NewCache(WithTTL[string, int](time.Second)) b := 1 c.Set(`a`, b) d, ok := c.Get(`a`) require.True(t, ok) require.Equal(t, b, d) time.Sleep(time.Second) d, ok = c.Get(`a`) require.False(t, ok) // 超时返回0值 require.Equal(t, d, 0) } ``` ### 实践3 集合操作 - 通过 set 做集合,可以给集合去重。可以给结合相并,想交,等操作。 - set 结构 github.com/weapons97/cache/set.go ```go func TestSetUnion(t *testing.T) { s := NewSet[string]() s.Add(`a`) s.Add(`b`) s2 := NewSet[string]() s2.Add(`b`) s2.Add(`d`) s3 := s.Union(s2) wantS3 := []string{`a`, `b`, `d`} ans := s3.List() sort.Strings(ans) require.Equal(t, wantS3, ans) spew.Dump(s.List(), s2.List(), s3.List()) } func TestSetJoin(t *testing.T) { s := NewSet[string]() s.Add(`a`) s.Add(`b`) s2 := NewSet[string]() s2.Add(`b`) s2.Add(`d`) s3 := s.Join(s2) wantS3 := []string{`b`} ans := s3.List() sort.Strings(ans) require.Equal(t, wantS3, ans) spew.Dump(s.List(), s2.List(), s3.List()) } func TestSetJoinLeft(t *testing.T) { s := NewSet[string]() s.Add(`a`) s.Add(`b`) s2 := NewSet[string]() s2.Add(`b`) s2.Add(`d`) s3 := s.JoinLeft(s2) wantS3 := []string{`a`, `b`} ans := s3.List() sort.Strings(ans) require.Equal(t, wantS3, ans) spew.Dump(s.List(), s2.List(), s3.List()) } func TestSetJoinRight(t *testing.T) { s := NewSet[string]() s.Add(`a`) s.Add(`b`) s2 := NewSet[string]() s2.Add(`b`) s2.Add(`d`) s3 := s.JoinRight(s2) wantS3 := []string{`b`, `d`} ans := s3.List() sort.Strings(ans) require.Equal(t, wantS3, ans) spew.Dump(s.List(), s2.List(), s3.List()) } func TestSetSub(t *testing.T) { s := NewSet[string]() s.Add(`a`) s.Add(`b`) s2 := NewSet[string]() s2.Add(`b`) s2.Add(`d`) s3 := s.Sub(s2) wantS3 := []string{`a`} ans := s3.List() sort.Strings(ans) require.Equal(t, wantS3, ans) spew.Dump(s.List(), s2.List(), s3.List()) } ``` - 通过set 去重 ```go // ShowImageInManifest 抓取 manifest 中imgs func ShowImageInManifest(manifest string) (imgs []string) { rx := regImages.FindAllStringSubmatch(manifest, -1) set := cache.NewSet[string]() for i := range rx { for j := range rx[i] { if strings.HasPrefix(rx[i][j], `image:`) { continue } tx0 := strings.TrimSpace(rx[i][j]) tx1 := strings.Trim(tx0, `'`) tx2 := strings.Trim(tx1, `"`) set.Add(tx2) } } imgs = set.List() return imgs } ``` #### 4 带索引的cache - 某些情况下,我们可能根据cache 的某个元素对cache进行遍历,这时候如果给cache 加上索引结构,可以对遍历加速。 - index 结构 github.com/weapons97/cache/index.go ```go type Person struct { id string lastName string fullName string country string } const ( IndexByLastName = `IndexByLastName` IndexByCountry = `IndexByCountry` ) func (p *Person) Indexs() map[string]IndexFunc { return map[string]IndexFunc{ IndexByLastName: func(indexed Indexed) (key []string) { ci := indexed.(*Person) return []string{ci.lastName} }, IndexByCountry: func(indexed Indexed) (key []string) { ci := indexed.(*Person) return []string{ci.country} }, } } func (p *Person) ID() (mainKey string) { return p.id } func (p *Person) Set(v interface{}) (Indexed, bool) { rx, ok := v.(*Person) if !ok { return nil, false } return rx, true } func (p *Person) Get(v Indexed) (interface{}, bool) { rx, ok := v.(*Person) if !ok { return nil, false } return rx, true } ``` ```go // 测试数据 var ( p1 = &Person{ id: `1`, lastName: "魏", fullName: "魏鹏", country: `China`, } p2 = &Person{ id: `2`, lastName: "魏", fullName: "魏无忌", country: `America`, } p3 = &Person{ id: `3`, lastName: "李", fullName: "李云", country: `China`, } p4 = &Person{ id: `4`, lastName: "黄", fullName: "黄帅来", country: `China`, } p5 = &Person{ id: `5`, lastName: "Cook", fullName: "TimCook", country: `America`, } p6 = &Person{ id: `6`, lastName: "Jobs", fullName: "SteveJobs", country: `America`, } p7 = &Person{ id: `7`, lastName: "Musk", fullName: "Elon Musk", country: `America`, } ) ``` ```go func TestIndexByCountry(t *testing.T) { index := NewIndexer(&Person{}) // set index.Set(p1) index.Set(p2) index.Set(p3) index.Set(p4) index.Set(p5) index.Set(p6) index.Set(p7) // search rs := index.Search(IndexByCountry, `China`) require.False(t, rs.Failed()) rx := rs.InvokeAll() require.Len(t, rx, 3) spew.Dump(rx) one := rs.InvokeOne().(*Person) require.Equal(t, one.country, `China`) spew.Dump(one) } // result === RUN TestIndexByCountry ([]interface {}) (len=3 cap=3) { (*cache.Person)(0x14139c0)({ id: (string) (len=1) "3", lastName: (string) (len=3) "李", fullName: (string) (len=6) "李云", country: (string) (len=5) "China" }), (*cache.Person)(0x1413a00)({ id: (string) (len=1) "4", lastName: (string) (len=3) "黄", fullName: (string) (len=9) "黄帅来", country: (string) (len=5) "China" }), (*cache.Person)(0x1413940)({ id: (string) (len=1) "1", lastName: (string) (len=3) "魏", fullName: (string) (len=6) "魏鹏", country: (string) (len=5) "China" }) } (*cache.Person)(0x14139c0)({ id: (string) (len=1) "3", lastName: (string) (len=3) "李", fullName: (string) (len=6) "李云", country: (string) (len=5) "China" }) --- PASS: TestIndexByCountry (0.00s) PASS ```

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